Question
What is the composition of lactulose?
| A. | Glucose + Galactose |
| B. |
Glucose + Fructose |
| C. |
Galactose + Fructose |
| D. |
Fructose + Ribulose |
Show Answer
|
Correct Answer � C Explanation |
 |
- Lactulose is a synthetic disaccharide composed of galactose and fructose.
- It is produced by isomerization of lactose (a natural sugar found in milk), where glucose in lactose is converted to fructose.
Mechanism and Uses of Lactulose:
-
In the Gut:
- Lactulose is not absorbed in the small intestine and reaches the colon, where it is metabolized by colonic bacteria into short-chain fatty acids (e.g., lactic acid, acetic acid).
- This lowers the colonic pH, creating an acidic environment.
-
Clinical Applications:
- Hepatic Encephalopathy: The acidic environment traps ammonia (NH₃) as ammonium ions (NH₄⁺), reducing systemic absorption and blood ammonia levels.
- Constipation: It acts as an osmotic laxative by drawing water into the bowel, softening stools, and promoting bowel movements.
Reasons to Rule Out Other Options:
A. Glucose + Galactose:
- Glucose and galactose form lactose, not lactulose.
B. Glucose + Fructose:
- Glucose and fructose form sucrose, a different disaccharide found in table sugar.
D. Fructose + Ribulose:
- This composition is not a disaccharide and does not describe lactulose.
